Heat exchanger

ABSTRACT

In a heat exchanger of the kind used for the transfer of heat from exhaust air, e.g. from rooms, to fresh air to be led into rooms, or for the transfer of heat the opposite way, means (9) for the cooled exhaust air are arranged after the outlet (4) with a view to transferring heat from the exhaust air to a heat reservoir (12), i.e. a heat pump circuit (10, 11). The thermodynamic efficiency is dependent on the difference in temperature, of course, and by transferring heat from exhaust air to for instance a water tank for hot water, the temperature being in some places close to the flow temperature of tap water, it will be possible to make use of much more of the latent heat of the exhaust air.

The invention relates to a heat exchanger in a house foreseen for thetransfer of heat from exhaust air into fresh air to be supplied to thehouse or the transfer of heat the opposite way whereby means for furthercolling the exhaust air are mounted after the outlet of the cooledexhaust air which means comprises a heat pump circuit.

A heat exchanger of that kind is known from the specification of SwissPat. No. 599 510 according to which the heat exchanger is used for therecovery of the heat of the air flowing out from the ventilating plantof a swimming bath. The means for further cooling the exhaust air afterthe heat exchanger itself comprises a liquid circulating system intendedto lead the heat from the exhaust air to a heat pump system by which theheat is led to another liquid circulating system transporting the heatto the place of use. Thus, four spots having heat transferring surfacesplus a heat pump circuit cause efficiency of heat transfer. And, thus,the total efficiency will be the product of five efficiencies.

The present invention is related to a development of the known heatexchanger, and the heat exchanger according to the invention ischaracteristic in that an evaporator is arranged in the flow of theexhaust air and that the condenser complete is placed in a water tankwhich is a tank holding hot tap water for the house.

Hereby only one heat pump circuit is required which is just possible asthe condenser is placed in a relatively cold place, i.e., preferably atthe bottom of the tank at the inlet for cold water. By such simple meansit is possible to achieve good efficiency of the heat pump circuiteither when temperature of the exhaust air is high or when there is coldwater around the condenser and especially in the event of both, i.e.,during firing periods. It is well-known that the higher difference oftemperature worked with the higher the efficiency of a thermodynamicprocess. The heat produced by the heat pump unit as waste heat stays inthe house, of course, and is utilized for heating. When the efficiencyof the systems gets too low, i.e., when the difference of temperaturebetween exhaust air and the water around the condenser is low, thepresent invention makes it possible to disconnect the heat pump circuitor stop it, whereby is contributed to improvement of the totalefficiency of the heat exchanger. All things considered it isdemonstrated that with the present construction it is possible toachieve very fine results for instance in a self-contained house usingan average amount of hot water under Danish climatic conditions. Duringfiring periods it will be possible that the temperature of the air ledinto the atmosphere is only about that of the outdoor air, and thusthere will be no losses. Therefore, this invention points to a heatexchanger which without serious losses offers constant renewal of theair in a house or an apartment housing a family.

Although it is indicated in the specification of the Swiss Pat. No. 599510 mentioned that the art known therefrom is applicable for the heatingof tap water, it does not mention the very simple means according to thepresent invention for achievement.

One embodiment of the invention is characteristic in that after theoutlet for fresh air an evaporator is arranged, which is connected tothe water tank in the same way as the first evaporator. This makes itpossible to use the heat exchanger as an air-conditioning plant insummer when outdoor temperature is higher than indoor temperature. Inthat case and according to the invention, the two evaporators may becharacteristic in that both evaporators are connected to the same heatpump circuit in a way leaving it optional whether one or the otherevaporator is connected to the circuit. Thus, only one heat pump circuitis required.

Finally, the heat exchanger may be characteristic in that it is across-flow heat exchanger having vanes or plates arranged to let theexhaust air pass once whereas it is arranged to let the suction air passonce through one half of the plates and then once through the other halfof the plates. This makes it possible to use the same fans and fanmotors for suction air and exhaust air respectively. During passagethrough the heat exchanger and past the evaporator changes of state ofcondition and thus changes of pressure of the air will of course occur.As only one evaporator will normally be in use, i.e., during firingperiods, viz. the one placed in the exhaust passage, wrong distributionof the pressure would result. By this embodiment the drawback isovercome.

The invention is explained with reference to the drawing where

FIG. 1 schematically shows an embodiment of a heat exchanger accordingto the invention,

FIG. 2 a development according to the invention,

FIG. 3 an embodiment of a heat exchanger according to the inventionbuilt together with a heat pump system and a hot-water tank into abox-shaped unit schematically seen from in front and one front platehaving been removed,

FIG. 4 a section along the line IV--IV of FIG. 3,

FIG. 5 a section along the line V--V of FIG. 3,

FIGS. 6, 7, and 8 a so-called "exploded" view of

FIG. 9 shows part of a plate heat exchanger of which FIGS. 6, 7, and 8show the three lower plates, FIG. 8 showing the bottom one, FIG. 7 thebottom plate but one, and FIG. 6 the third from the bottom.

In FIG. 1 is shown a box-shaped unit 1 containing a so-called cross-flowheat exchanger 2 for air and two fans 2 and 4. The fan 3 sucks fresh airfrom an inlet 5 through the heat exchanger 2 and blows it out through anoutlet 6, whereas the fan 4 sucks exhaust air from a room from anotherinlet 7 through the heat exchanger 2 and blows it out through an outlet8. In the outlet 8 an evaporator 9 is arranged forming part of a heatpump circuit consisting of a compressor 10 and a condenser coil 11arranged in a water tank 12 with an inlet 13 and an outlet 14. Often,the tank 12 will be placed at some distance from the other elements ofthe constructions, and in that case the pipes will be insulated.

Now, the heat exchanger operates in the following manner provided thatthe fresh air is colder than the exhaust air which will be the case inwinter. The exhaust air sucked in through the inlet 7 will liberate heatin the cross-flow heat exchanger 2, which is in part, i.e. with acertain efficiency, transferred to the fresh air sucked in through theinlet 5. The heated fresh air is blown through the outlet 6 to rooms notshown whereas the cooled exhaust air is led through the outlet 8 forfurther cooling when passing the evaporator 9 before being led into theopen air. The heat removed by the evaporator 9 is by the compressor 10pumped into the tank 12 where it will through the condenser coil 11liberate into the water preferably in the coldest water at the bottomand near the inlet 13.

FIG. 2 shows a development of the heat exchanger according to FIG. 1 andwhere the elements of the construction shown again carry the samereference numbers. The difference consists in a further evaporator 15having been built into the outlet 6 connected parallelly to the otherevaporator 9 and valves 16 and 17 being arranged in the heat pumpcircuit making it possible to switch on one evaporator or the other. Incase of the outdoor temperature being higher than that of the rooms tobe supplied with fresh air, and the evaporator 15 being on, it will bepossible to cool the fresh air before it is led into the rooms, and atthe same time the water in the tank 12 is heated. The heat exchanging inthe cross-flow heat exchanger 2 will in that case be in the oppositedirection.

In both cases the heat collected by evaporators 9 and 15 is the heat nottransformed in the cross-flow heat exchanger 2 as its efficiency willnever be 100%.

Around the tank may be arranged a jacket 18 with an access 19 and anexit 20. The heat exchanger thus established is applicable for heating.

FIGS. 3, 4, and 5 are to be look upon in combination, and the items ofthese three figures carry the same reference numbers.

FIG. 3 shows a unit in which a hot water tank 21 is arranged. Above thetank a box-shaped plate heat exchanger 22 of square section is arrangedon its edge. The hot water tank 21 and the plate heat exchanger 22 areinter-connected by a heat pump system consisting of a heat pump 23 andan evaporator 24 arranged along one of the fan sides 25 in the heatexchanger. Along the same side cooled air from the room is flowing, theair being let in through the opposite, rectangular side 26, see arrow 27in FIG. 3 and arrow 28 in FIGS. 3 and 5. The air is supplied by a fan 29which is connected with a room in a house. When passing through the heatexchanger 22 and the evaporator 24 the air is cooled to a temperaturewhich will often be only a couple of degrees above temperature ofatmosphere. After the evaporator 24 the air is led into the atmosphereas shown by arrows 30, 31, and 32.

Fresh atmospheric air is taken in through an inlet 33 and led through afan 34 towards one half 35 of the side 36 of the heat exchanger 22 atwhich side 36 a triangular screen 37 is arranged. In order to clearlyshow the position of the triangular screen 37 its sides carry thereferences a, b, and c in the three figures. When the fresh air hasflown through half of the heat exchanger 22 it will reach the room 38which is a closed room. From there it is pressed through the other halfof the heat exchanger as shown by dotted arrow 39, and the air will comeout on the other side of the triangular plate 37, thus. In this roomheating elements--not shown for the sake of clearliness--are arranged.The air is led into the room of the house through the outlet 41.

FIG. 6 shows a square plate 41 having two upward bent edges 42 and 43opposite each other, and two downward bent edges 44 and 45. FIG. 7 showsthe same but rotated 90° and the two upward bent edges 46 and 47 beingintended for adhesion to the edges 44 and 45 respectively. Adhesionaccording to this principle makes it possible to build a plate heatexchanger as shown in FIG. 9 and applicable in the constructionaccording to FIGS. 3, 4, and 5.

The invention is widely variable. Thus, it is clear that in principlethe cross-flow heat exchanger 2 may be a heat exchanger of any kind. Forthe sake of clearliness, no throttles are shown in the heat pump andcooling circuits shown, but of course there are such throttles.

I claim:
 1. A heat exchanger system in a house arranged for the transferof heat from exhaust air into fresh air to be supplied to the house orthe transfer of heat in the opposite manner comprising means forcreating a flow of exhaust air from the interior of the house, means forfurther creating a flow of fresh air from the outside to the interior ofthe house, means arranged to receive said exhaust flow and create a heatexchange relationship with the flow of fresh air, means connecteddownstream of said heat exchanger means for further cooling the flow ofexhaust air exiting therefrom said further cooling means includes a heatpump circuit, said heat pump circuit having an evaporator being arrangedin the flow of the exhaust air from said heat exchanger means and acondenser operatively connected to said evaporator and wholly submergedin the water of a water tank which is a tank holding hot tap water forthe house, said condenser heating the tap water of the tank in responseto the action of said condenser cooling the flow of exhaust air.
 2. Aheat exchanger according to claim 1, whereby the inlet for cold watersupplying the tap water is placed at the bottom of the tank, saidcondenser is further placed at said bottom.
 3. A heat exchangeraccording to claim 1 or 2 further including means for connecting anddisconnecting the heat pump circuit on demand.
 4. A heat exchangeraccording to claim 1, 2 or 3, wherein said means for creating a flow offresh air directs said outside air through said heat exchanger means, asecond evaporator arranged to receive the flow of fresh air exiting fromsaid heat exchanger for further cooling, and said second evaporatorbeing connected to a condenser wholly submerged in the water of thewater tank.
 5. A heat exchanger according to claim 4, wherein both ofsaid evaporators are connected to the same heat pump circuit, and meansconnected to said means for selectively operating said first and secondevaporators of said pump circuit in a way leaving it optional whetherone or the other evaporator is connected to the circuit.
 6. A heatexchanger according to claim 1, wherein said heat exchanging meansincludes a cross-flow heat exchanger having a plurality of platesarranged to let the flow of exhaust air pass therethrough and arrangedto let the flow of fresh air pass through one half of the plates to bedirected to the interior of the house and then back through the otherhalf of the plates, said flow of exhaust air and fresh air beingaccordingly arranged in heat exchange relationship.